Death's mansion is a large mansion owned by Harold Death Esquire, more commonly known as simply Death or the Grim Reaper. It is located in his own realm, and is where the psychopomp and his pet dog Muncher spend their time when not reaping souls. Death's office is connected to the mansion, although players cannot use one to access the other.

The mansion has been accessible during the 2007, 2009, 2010 and 2014 Hallowe'en events. It has been primarily accessed through a dark house portal to the south of Falador, although in 2014 it was instead accessed by talking to Muncher next to the Burthorpe lodestone. It appeared significantly different in 2007, but its appearance has remained relatively consistent since 2009.

The mansion is decorated with a number of pumpkins, candles, and Death clocks. It has a number of bookcases, containing books such as The Seven Habits of Highly Effective Reapers. The ground floor also contains a range, although it doesn't see much use. The first floor contains two bedrooms and a bathroom. The larger of the two bedrooms presumably belongs to the reaper himself, with the smaller belonging to his current servant. Minstrel Web took up residence inside his bathroom during the 2009 event.